Caselli V M, Savenije T J
Department of Chemical Engineering, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, The Netherlands.
J Phys Chem Lett. 2022 Aug 18;13(32):7523-7531. doi: 10.1021/acs.jpclett.2c01728. Epub 2022 Aug 10.
To increase the open-circuit voltage in perovskite-based solar cells, recombination processes at the interface with transport layers (TLs) should be identified and reduced. We investigated the charge carrier dynamics in bilayers of methylammonium lead iodide (MAPbI) with C60 or Spiro-OMeTAD using time-resolved microwave conductance (TRMC) measurements with and without bias illumination (BI). By modeling the results, we quantified recombination losses in bare MAPbI and extraction into the TLs. Only under BI did we find that the density of deep traps increases in bare MAPbI, substantially enhancing trap-mediated losses. This reversible process is prevented in a bilayer with C60 but not with Spiro-OMeTAD. While under BI extraction rates reduce significantly in both bilayers, only in MAPbI/Spiro-OMeTAD does interfacial recombination also increases, substantially reducing the quasi Fermi level splitting. This work demonstrates the impact of BI on charge dynamics and shows that adjusting the Fermi level of TLs is imperative to reduce interfacial recombination losses.
为了提高钙钛矿基太阳能电池的开路电压，需要识别并减少与传输层（TLs）界面处的复合过程。我们使用时间分辨微波电导（TRMC）测量方法，在有偏压光照（BI）和无偏压光照的情况下，研究了甲基碘化铅（MAPbI）与C60或Spiro-OMeTAD双层中的电荷载流子动力学。通过对结果进行建模，我们量化了裸MAPbI中的复合损失以及向传输层的提取。仅在有偏压光照的情况下，我们发现裸MAPbI中的深陷阱密度增加，显著增强了陷阱介导的损失。在与C60的双层中，这种可逆过程被阻止，但与Spiro-OMeTAD的双层中则没有。虽然在有偏压光照下，两个双层中的提取率都显著降低，但只有在MAPbI/Spiro-OMeTAD中，界面复合也会增加，从而大幅降低准费米能级分裂。这项工作证明了偏压光照对电荷动力学的影响，并表明调整传输层的费米能级对于减少界面复合损失至关重要。
